1. Field of the Invention
The present invention relates to multi-band wireless communication systems, and particularly to a reconfigurable MIMO and sensing antenna system that has a two-element reconfigurable antenna and a ground plane serving as an ultra-wide band (UWB) sensing element for use in compact wireless devices and LTE mobile handsets. The complete setup can be used in radio frequency-based applications, including 4G cellular systems.
2. Description of the Related Art
In modern wireless communications, the exponential growth of wireless services results in an increasing demand of the data rate requirements and reliability of data. These services may include high-quality audio/video calls, online video streaming, video conferencing and online gaming. These demanding features may require wide bandwidth operation or covering operation across several frequency bands. This provides motivation for comprehensive and efficient utilization of the available spectrum. The effort to overcome inefficient and highly underutilized spectrum resources has led to concept of cognitive radio (CR). A CR system is based on structural design of software-defined radio intended to enhance spectrum utilization efficiency by interacting with the operating environment. A CR-based system must be aware of its environment by sensing spectrum usage and have the capability to switch over the operating points among different unoccupied frequency bands. A CR-based system may cover various features, including sensing the spectrum of nearby devices, switching between different frequency bands, and power level adjustment of transmitting antennas,
Reconfigurable antennas are able to change their operating fundamental characteristics, e.g., resonance frequency, radiation pattern, polarization and impedance bandwidth. A frequency reconfigurable antenna is an essential component of CR platforms. An attractive feature of such an antenna is its switching across several frequency bands by activating different radiating parts of the same antenna. Reconfigurability is the fundamental requirement for CR platforms. CR-based systems are capable of switching the frequency bands of a single frequency reconfigurable antenna over different bands to efficiently and inclusively utilize idle spectrum.
To achieve the desired characteristics of reconfigurability and desired performance of a MIMO antenna system, several challenges need to be overcome. These issues include the size of the antennas for low frequency bands; a requirement of high isolation between closely spaced antennas; and control circuitry embedded within the given antenna to achieve the desired reconfiguration. Moreover, the performance of the MIMO system degrades significantly for closely spaced antennas due to high mutual coupling.
Thus, a reconfigurable MIMO and sensing antenna system solving the aforementioned problems is desired.